The production of halogens from aqueous solutions (or other dispersions including even slurries) of their corresponding acids or alkali metal salts and the like by electrolysis thereof in electrolytic diaphragm or equivalent separator cells is well known and widely practiced. Improved techniques to accomplish such production include utilization of oxidizing gas depolarized cathodes in the involved halogen-manufacturing cell units. The manufacture of caustic soda and chlorine from common salt is a good illustration and a particularly important application of this type means for making halogens and associated co-products.
Various aspects relevant to the use of oxygen or oxygen depolarized cathodes in electrolytic cells are amply demonstrated in, inter alia, U.S. Patents and Patent Reference Nos. 1,474,594; 2,273,795; 2,681,884; 3,035,998; 3,117,034; 3,117,066; 3,262,868; 3,276,911; 3,316,167; 3,507,701; 3,544,378; 3,645,796; 3,660,255; 3,711,388; 3,767,542; 3,923,628; 3,926,769; 3,935,027; 3,959,112; 4,035,254; and 4,035,255, all herein incorporated by reference.
It has been observed, however, that in order to employ an oxygen or the like electrode as a depolarized cathode in a chlor-alkali or equivalent diaphragm or equivalent separator cell, it is advantageous for the separator element to be maintained and supported for operation so as to actually be spaced a short distance from the cathode in order to better accommodate gas transport to the cathode while maintaining the electrolyte solution on one side of the cathode and the gas on the other side. This is the case with asbestos diaphragms, ion exchange membranes or anything similar or analogous thereto. It is especially so when a drawn asbestos diaphragm is to be used which, for practical purposes, is better deployed when mounted on a rigid support. While metallic screens, grids or the like foraminous metal constructions are ostentatiously well suited for utilization as support elements or backing members for asbestos diaphragms, they are ordinarily not employed for the purpose. This is because of the disadvantageous fact that under normal operating conditions of a typical electrolytic diaphragm cell, a metallic diaphragm support element frequently and sometimes unpredictably tends, with most undesirable and unwanted results, to become and function as an electrode due to bipolar effects which arise and materially influence metallic support behavior.
The basic characteristics and operational principles and limitations of electrolytic diaphragm and ion exchange membrane cell practice are so widely comprehended by those skilled in the art that further elucidation thereof and elaboration thereon is unnecessary for thorough understanding and recognition of the advance contributed and made possible to achieve by and with the development(s) of the present invention.